Rectifier for wireless television reception



Jan. 26, 1937. K. SCHLESINGER 2,068,769-

RECTIFIER FOR WIRELESS TELEVISION RECEPTION Filed Oct. 17, 1934 Axis ofMe Primar 57/? van 1 00:

Patentecl Jan. 26, 1937 PAT E NT F F I (J-E RECTIFIER FOR. WIRELESSTELEVISION RECEPTION Kurt Schlesinger, Berlin, Germany ApplicationOctober 17, 1934, Serial No. 748,644 In Germany October 21, 1933 6Claims.

When employing the principle of push-pull audion connection fortelevision reception purposes as set forth in the patent applicationSer. No. 735,600, Patent No. 2,029,640, February 4, 1936, it is acharacteristic feature that the grid circuit coil of the counter-cadenceaudion is raised to high-frequency potential against earth. The carrierwave disappears in the anode circuit of this audion only when the twogrids receive as compared with the earthed cathode an equal but opposedcarrier frequency potential.

The present invention is relative to an audion arrangement such asdescribed above and constitutes an improvement of the connection deviceof the above mentioned patent application with respect to constructionand arrangement of the primary and secondary circuits of the transformerconnected to the input of said audion valve.

The invention will be best understood with reference to the accompanyingdrawing, in which Fig. 1 shows an exemplary scheme of-a countercadenceaudion arrangement,

Fig. 2 an exemplary embodiment of the transformer employed in theconnection system, while in Fig. 3 a scheme of the radii of the windingsof said transformer is indicated.

With reference to Fig. 1 a grid circuit coil I constituting thesecondary of a high frequency transformer is provided. The ends of saidsecondary are connected to the two grids 4 and 5 of a twin grid valvepreferably possessing a screening grid and an anode 2, which isconnected to the anode potential over the resistance 3. It is now theobject of the invention to make the carrier wave disappear in the anodecircuit of this audion valve.

This object may be accomplished without increase of the earth capacityof the total grid circuit, which according to the invention is reducedto a minimum. For this purpose, according to the invention, the primarycoil 1 of the amplifier tube 8 is continued in the form of an additionalwinding 9 running in the same direction. There is then produced at thefreely oscillating end of 9 a potential, which with the same number ofwindings is equal but opposed, in the case of no load, to the potentialat the anode of 8. In this connection it is taken for granted accordingto the invention that the coils I and 9 are firmly coupled. This isaccomplished by winding both coils I and 9 on the same cylinder. Ato-roid arrangement as shown in Fig. 2 is particularly favorable, inwhich arrangement the coils 1 and 9 are situated on a ring, over whichthere may be placed the coil I. It may then be accomplished that throughthe medium of the stray capacities I0 and II between the primary andsecondary windings potentials of opposite sign take effect on the gridlines of the coil I, the ratio thereof being adjustable by displacement.There may ac.- cordingly be found a position of the will in relation toI and@ in which the desired object is accomplished, viz., the centre ofI earthed dynamically in respect of the carrier frequency. The middle ofthe coils I and9 is short-circuited to earth over a condenser I2 ofapproximately 10,000 cm. or more, whilst the tube :8 is supplied withanode current through the medium of a resistance I3.

The capacities I0 and II represent in themselves an additional load forthe circuit ofthe demodulated potentials. According to the invention,the same are made assmall as possible by sufficient spacing between theprimary and secondary windings. If, as usually necessary in the case ofsensitive receiving apparatus, an earthed shield is placed over thetransformer, there are preferably arranged within this shield I4, Fig.3, which has the radius 114, the primary winding I5 as outer and thesecondary winding I6 asinner winding, provision being made for asufficient spacing, for example, at least 5 mm., between I5 and-I6. Byusing very thin wire for IS the total surface with given self-inductionmay be made very small. If the reversed arrangement is employed, i. e.,with the primary coil inside and the secondary coil outside, there isfound in respect of the secondary winding a minimum of the resultingcapacity against earth if, in accordance with the invention, thefollowing equation is taken with regard to the radius:

In ,Fig. 1 there are included three resistances II, I8 and I9. In thisrespect, in the connection of this resistance T-member as shown, merelythe resistances II and I8 serve to damp the secondary coil I, whilst theresistance I9 serves solely for leakage of the grid circuit charges. Ina connection of the three resistances other than that shown thisseparation of the functions would not be ensured, for which reason theconnection in the drawing is particularly advantageous for theindependent adjustment of damping and leakage. The resistances I! and I8are equal to each other, and are selected in such fashion that they justattenuate the natural oscillation of the circuit formed by I and itsparallel capacities sufficiently to avoid plasticity in the televisionimage (order of magnitude approximately 10,000 ohms). According to theinvention, the natural oscillation of the coil I is so selected that itapproximately coincides with the lower side band of the modulatedcarrier wave. The resistance I9 is so chosen that the time constant ofthe total capacity-to ground .parallelato I9 is smaller than theduration of an image .point (order of magnitude of I9 approximately40,000

ohms in the case of tubes having the grids 4 and 5 passed out).

I claim:

1. A push pull detector arrangement, more particularly for televisionpurposes comprising a. twin grid tube connected to the output circuit ofan amplifier stage, a high frequency input transformer consisting of aprimary winding and a secondary winding, said primary winding beingdivided into two halves, one end of the one of said halves beingconnected to the anode of said preceding amplifier stage and theconnection point of said two halves being connected to the cathode ofthe preceding amplifier stage, the ends of said secondary coil beingconnected each to one of said grids of said tube, an audion resistance,a middle tapping point at said secondary winding being connected to thecathode of said tube and to earth by means of said audion resistance,and two damping resistances connected across said ends of said secondarywindings and said tapping point, the other one of said halves of saidprimary winding being wound in the same direction as the one half ofsaid primary, said other one of said two halves forming a freelyoscillating system, the end of said other half not connected to said onehalf being a free end.

2. A push pull detector arrangement, more particularly for televisionpurposes comprising a twin grid tube connected to the output circuit ofan amplifier stage, a high frequency input transformer consisting of aprimary winding and a econdary winding, said primary winding beingdivided into two halves, one end of the one of said halves beingconnected to the anode of said preceding amplifier stage and theconnection point of said two halves being connected to the cathode ofthe preceding amplifier stage, the ends of said secondary coil beingconnected each to one of said grids of said tube, an audion resistance,a middle tapping point at said secondary winding being connected to thecathode of said tube and to earth by means of said audion resistance,and two damping resistances connected across said ends of said secondarywindings and said tapping point, the other one of said halves of saidprimary winding being wound in the same direction as the one half ofsaid primary, said other one of said two halves forming a freelyoscillating system, the end of said other half not connected to said onehalf being a free end, said two halves of said primary being firmlymagnetically coupled to each other.

3. A push pull detector arrangement, more particularly for televisionpurposes comprising a twin grid tube connected to the output circuit ofan amplifier stage, a high frequency input transformer consisting of aprimary winding and a secondary winding, said primary winding beingdivided into two halves, one end of the one of said halves beingconnected to the anode of said preceding amplifier stage and theconnection point of said two halves being connected to the cathode ofthe preceding amplifier stage, the ends of said secondary coil beingconnected each to one of said grids of said tube, an audion resistance,a middle tapping point at said secondary winding being connected to thecathode of said tube and to earth by means of said audion resistance,and two damping resistances connected across said ends of said secondarywindings and said tapping point, the other one of said halves of saidprimary winding being wound in the same direction as the one half ofsaid primary, said other one of said two halves forming a freelyoscillating system, the end of said other half not connected to said onehalf being a free end, said two halves of said primary being firmlymagnetically coupled to each other, said transformer being constructedas a toroid.

4. A push pull detector arrangement, more particularly for televisionpurposes comprising a twin grid tube connected to the output circuit ofan amplifier stage, a high frequency input transformer consisting of aprimary winding and a secondary winding, said primary winding beingdivided into two halves, one end of the one of said halves beingconnected to the anode of said preceding amplifier stage and theconnection point of said two halves being connected to the cathode ofthe preceding amplifier stage, the ends of said secondary coil beingconnected each to one of said grids of said tube, an audion resistance,a middle tapping point at said secondary winding being connected to thecathode of said tube and to earth by means of said audion resistance,and two damping resistances connected across said ends of said secondarywindings and said tapping point, the other one of said halves of saidprimary winding being wound in the same direction as the one half ofsaid primary, said other one of said two halves forming a freelyoscillating system, the end of said other half not connected to said onehalf being a free end, said two halves of said primary being firmlymagnetically coupled to each other, said transformer being constructedas a toroid, said primary windings and said secondary possessingcylindrical shape, being shielded and arranged one in another, the radiiof the windings and the shield being so dimensioned in relation to eachother as to obtain a minimum of the resulting earth load of thesecondary.

5. In a high-frequency transmission circuit a transformer for couplingan output-circuit of an amplifier stage to a push-pull connectioncircuit, comprising a primary and secondary winding, said primarywinding being divided into two halves, one half being connected betweenthe anode and the cathode of said amplifying stage, the other one beingwound in the same direction as the one half and forming a freelyoscillating system, the end of said other half not connected to said onehalf being a free end, said two halves of the primary being firmlymagnetically coupled to each other, said secondary winding beingarranged in a push-pull-circuit-connection and adjustable in itssituation relative to said primary winding.

6. In a high-frequency transmission circuit a transformer for couplingan output-circuit of an amplifier stage to a push-pull connectioncircuit, comprising a primary and secondary winding, said primarywinding being divided into two halves, one half being connected betweenthe anode and the cathode of said amplifying stage, the other one beingwound in the same direction as the one half and forming a freelyoscillating system, the end of said other half not connected to said onehalf being a free end, said two halves of the primary being firmlymagnetically coupled to each other, said secondary winding being ar--ranged in a push-pull-circuit-connection and adjustable in its situationrelative to said primary winding, said transformer being constructed asa toroid.

KURT SCI-ILESINGER.

